Recovery of refractory metal values

ABSTRACT

Refractory metals such as vanadium are recovered from aqueous solutions containing the metal in the form of the oxide by adding to the solution a ferric salt and an ammonium salt of common anion, and a quantity of finely divided carbon. The vanadium is precipitated in the form of an iron-vanadium oxide complex in intimate admixture with the finely divided carbon. The admixture is recovered and can be reduced to produce a ferro-refractory metal-carbon alloy suitable for use as an additive in steelmaking.

United States Patent 11 1 Vojkovic 1 51 Sept. 11, 1973 1 RECOVERY OFREFRACTORY METAL VALUES [75] Inventor: Milos Vojkovic, Libertyville,Ill.

[22] Filed: June 18, 1971 [21] Appl. No.2 154,686

52 us. c1 423/56, 423/58, 423/67, 423/71, 423/81, 423/143, 423/140,75/123,

511 1m. 01.. C0lg 23/00, COlg 25/00, COlg 31/00, COlg 33/00, COlg 39/00,COlg 41 00 [58] Field of Search 23/15 w, 19 v, 18, 23/19, 22-24; 75/108,123, 129; 423/56, 58,

[56] References Cited UNITED STATES PATENTS 3,440,035 4/1969 Iwase etal. "75/108 X 1,250,063 1l/l917 Westling et aI. 23/15 W 1,292,559 l/19l9Andersen et al 23/15 W FOREIGN PATENTS OR APPLICATIONS 1,925,983 1l/l969Germany 23/15 W Primary Examiner-Herbert T. Carter Attorney-James E.Wolber et a1.

57 ABSTRACT Refractory metals such as vanadium are recovered fromaqueous solutions containing the metal in the form of the oxide byadding to the solution a ferric salt and an ammonium salt of commonanion, and a quantity of finely divided carbon. The vanadium isprecipitated in the form of an iron-vanadium oxide complex in intimateadmixture with the finely divided carbon. The admixture is recovered andcan be reduced to produce a ferns-refractory metal-carbon alloy suitablefor use as an additive in steel-making.

21 Claims, No Drawings 1 RECOVERY OF REFRACTORY METAL VALUES BACKGROUNDOF THE INVENTION Refractory metals, namely vanadium, molybdenum,tungsten, titanium and niobium, are useful alloying elements insteel-making. Refractory metals are desirably incorporated into thesteel in a form which is preferably dense and readily soluble in molteniron. Usually these elements are added in the form of a ferro-alloywhich desirably contains a major portion of the refractory metal andminor portions of iron and carbon.

Since there exists only limited quantities of highgrade concentrates ofrefractory materials, and since the beneficiation of minerals containingthese elements is generally costly and inefficient, it has been proposedto treat chemically the primary raw material containing the refractorymetal, usually to solubilize the refractory metal values in the rawmaterial, and then recover the refractory metal values in a formsuitable for use or for further processing. Exemplary of such priorpractice is the recovery of vanadium values from vanadiumbearing slag.The slag is crushed, ground, and typically admixed with an alkalinematerial suchas soda ash or sodium carbonate. The admixture is roastedto place the vanadium values mainly in the formof V,O,, and the roastedslag is leached with water or an aqueous liquor to extract the vanadiumvalues as an alkali vanadate. The resulting aqueous liquid may betreated, if desired, to remove impurities, and the vanadium values areprecipitated by the addition of a suitable complexing agent such asferric sulfate.

Other processes are known in which a roasted vanadium ore is leachedwith a mineral acid to solubilize the vanadium values, followed by asimilar precipitation step. The recovered vanadium-containingprecipitate is reduced, usually in the presence of carbon and iron, toform a useful vanadium steel-making additive.

Similar processes are applicable to the other refractory metals,especially molybdenum and tungsten.

This invention relates to an improved process for the recovery ofrefractory metal values from aqueous solu' tion. The recovered valuesare ina form especially adapted for further processing to produce arefractory metal additive which is particularly useful in steelmaking.

DESCRIPTION OF THE INVENTION ln accordance with this inventionrefractory metal values are recovered from aqueous solution whichcontains such values largely in the highest state of oxidation, i.e.,pentavalent state for vanadium and hexavalent state for tungsten andmolybdenum. By this it is meant that not less than about 80 percent ofthe refractory metal values are in the highest state of oxidation.

The presence of small amounts of'values in a lower nium to refractorymetal mass ratio in the range of 0.05:1.0 to 1.5:].0. Finely dividedcarbon is preferably added to the solution in an amount to provide acarbon to refractory metal mass ratio in the range of 0.6:].0 to 0.8:].0and thoroughly dispersed throughout the solution. An iron-refractorymetal complex is then precipitated, preferably at a pH in the range ofabout 2.5 to 4.0, and the precipitated complex and carbon are recoveredfrom the solution in intimate admixture by filtration or centrifugation.The temperature of precipitation is not critical, temperatures betweenambient and the boiling point of the solution being satisfactory, withabout 60C. being preferred.

The recovered admixture of carbon and refractory metal-iron complex maybe dried and reduced by known techniques to provide a desirablesteel-making additive.

In some instances, because of product specifications requiring highvanadium content, the quantity of ferric salt added may be less thanadequate to provide desired refractory metal recoveries. In suchinstances the aqueous liquor separated from the precipitated refractorymetal-containing complex will be further processed by adding additionalamounts of ferric salt. Dueto the relatively low concentrations ofrefractory metal in this liquor, the addition of moderate quantities offerric salt will result in very high iron to refractory metal massrotios, resulting in the precipitation of further quantities ofrefractory metal as an iron-refractory metal complex. This complex,which may be too high in :iron and too low in refractory metal toprovide a suitable product, is separated from the aqueous liquor asbefore described. Advantageously, the precipitated complex isdissolvedin an aqueous solution of strong mineral acid, preferably amineral acid of common anion with the aforesaid ferric salt, andrecycled to the initial precipitation step of the process. In thismanner recovery of refractory metal values is substantially increased,with the recycle further providing some or all of the ferric saltrequired for the initial precipitation.

Where the raw material used in the process is at least in part an acidicaqueous liquor containing refractory metal values,'this acidic aqueousliquor advantageously provides the aqueous solution of strong mineralacid in which the secondary precipitated iron-refractory metal complexis dissolved.

The process of this invention is applicable to the purification andrecovery of vanadium, molybdenum, tungsten, titanium, and columbium. Theinvention will be specifically illustrated with reference to thepurification and recovery of vanadium.

EXAMPLE I Fuel ash residue was used as the primary raw vanadium source.The fuel ash residue assayed 66.4% V 0 4.62% Fe, 5.73% 810,, 0.10% P 01.38% C00, and

0.58% MgO.

This ash residue was processed by known technology to'yield analkalineliquor containing 84.93 gramsper liter of vanadium calculated as V 0 andan acidic liquor containing 6.07 grams per liter of vanadium calwaswashed with 1% aqueous ammonium chloride and dried at about 105C. Theloss on drying was 69.1 percent. The combined filtrate and wash wateranalyzed 0.18 grams per liter of V The overall recovery of vanadiumbased upon the content of the admixed aqueous alkaline and acidsolutions was 99.1 percent.

THe dried product of the foregoing example was reduced at an elevatedtemperature to produce a substantially oxygen-free metallic productsuitable for use as a steel-making additive.

The foregoing example was repeated using the same admixture of alkalineand acidic vanadium-containing solutions, but with the addition ofamounts of carbon, ferric sulfate, and ammonium sulfate to provide thecarbon to vanadium, iron to vanadium, and ammonium to vanadium massratios hereinafter specified in Table 1. The results of the experimentand the character of the metallic additive produced by reduction of thedried, recovered vanadium precipitate complex are set forth in Table 1.

Example 1. The 0.3 liter of acidic solution is then combined withanother 1.0 liter of the alkaline solution described in Example I. Theprimary precipitation is then repeated after adding additionalquantities of ferric sulfate, ammonium sulfate and carbon to provide theiron to vanadium, ammonium to vanadium, and carbon to vanadium ratios ofTest A-4. The primary precipitation is again carried out as described inExample 1, Test A-4.

EXAMPLE 111.

A molybdenite concentrate assaying approximately 35 percent molybdenumand 2-3 percent copper was employed as a primary raw material for thepreparation of aqueous solutions of molybdenum. The raw material wasprocessed by known means as in Example 1 to yield an alkaline solutioncontaining 91.3 grams per liter of molybdenum (calculated as M0) and anacidic solution containing 20.5 grams per liter of molybdenum(calculated as M0). The recovery of molybdenum at this stage was 98.43percent of the molybdenum contained in the molybdenite concentrate.

The molybdenum-containing solutions were admixed in the ratio of 1 literof alkaline solution to 1 liter of acidic solution and to the admixturewas added ferric sulfate in an amount to provide 11.2 grams of Fe.

The pH of the resulting slurry was about 1.8 and-was adjusted to a valueof 3.5 by the addition of aqueous ammonia. The resulting solution wasagitated for TABLE 1 Reduced vanadium additive Percent Precipitationmass ratios reeogreziy Percent m n Fe+++/V NIL /V C/V solution V Fe O 0ON 0.110 1.63 0. 71 91. 0 72. 2 7. 6 16. 46 0.30 0. 21 0. 108 1. 61 0.76 92. 7 75. 8 7. 5 18. 02 0. 0. 24 0. 163 1.07 0.65 92. 1 76. 1 12. 113.80 0.46 0. 18 0. 163 1.06 0.70 92.3 75. 5 11. 7 14. 61 0. 43 0. 19 0.239 1. 13 0. 72 93. 8 69. 9 15. 4 13. 61 0. 73 0. 19 0. 234 1. 11 0. 7696. 5 69. 5 16. 6 14. 67 0.78 0.21 0. 320 1. 28 0. 68 96. 0 64. 2 21. 413. 56 0. 47 0. 21 9. 310 1.27 0. 72 97. 1 64. 1 21.5 15.04 0. 42 0. 230. 64 1. 18 0. 68 96. 5 56. O 35. 8 7. ()0 0. 42 0. 13 0.61 1. 19 0. 7198. 7 55. 7 34. 9 11. 29 0. 19 0.20 0. 86 0. 28 0. 79 93. 1 47. 6 46. 07. 15 0. 57 0. 15 0. 85 0. 27 0. 81 94. 5 47. 8 46. 4 7. 66 0. 43 O.16 1. ()0 0.32 0. 82 99. 9 45. 8 50. 3 5. 57 0. 79 0. 12 1. ()0 0.320.85 99. 9 44. 6 50. 7 6. 39 O. 48 0. 14 1. 23 nil 0. 78 99. 9 42. 0 50.8 8. 34 0. 80 0. 20 1. 37 nil 0. 82 99. 9 40. 3 49. 6 13. 05 0. 34 0. 32

EXA M PLE II.

The vanadium recovery of 91 percent obtained in Test A-4 of Table 1 isconsidered inadequate. Accordingly, the aqueous liquor separated fromthe precipitated vanadium complex, which liquor contains about 8.2 gramsof vanadium calculated as V 0 is treated by the addition of ferricsulfate in an amount equal to that used in the initial precipitationstep of Test A-4, i.e., an amount sufficient to provide an iron tovanadium mass ratio of 1.22 to 1.00 in the separated aqueous liquor.

The solution is agitated for a period of 1 hr. and filtered withsuction. The solid residue contained about 8.1 grams of vanadium,calculated as V 0 together with most of the added iron.

The precipitate is dissolved in a second 0.3 liter of the acidicvanadium-containing solution described in minutes, and the resultingslurry was filtered using suction and the solids washed with watercontaining 1% ammonium chloride. The solids were removed and dried at105C. to give a loss on drying of 75.5 percent; The combined filtrateand wash analyzed 2.63 grams per liter molybdenum.

The dried solids, containing 94.04 percent of the molybdenum initiallypresent in the alkaline and acidic solutions were found upon analysis tocontain 1 33.69% molybdenum, 12.14% Fe, 0.032% Cu, and 0.106% Si.

The dried solids were reduced at an elevated temperature with a loss inweight of 53.63 percent to produce a metallic additive suitable for usein steel-making. The

additive analyzed:

Mo 72.49 percent Fe 26.10 percent Cu 0.07 percent S 0.1 percent Si 0.23percent 0.59 percent EXAMPLE IV A scheelite concentrate analyzed 72.61%W0 0.3% Sn, 0.05% P, 0.36% S, 19.25% CaO, 0.37% Mo, 0.06% Mn, 1.12% Fe;and a wolframite concentrate assaying 66.5% W0 2.13% SiO,25.00% FeO,0.08% P, and 0.014% S, were used as primary raw tungsten sources. Bothraw materials were processed by known means to give ultimately asolution of ammonium tungstate containing 76.5 grams per liter tungsten(calculated as W). The recovery of tungsten at this stage was 97.9percent of the tungsten contained in the scheelite concentrate and 90.9percent of the tungsten contained in the wolframite concentrate.

The ammonium tungstate solution was treated at ambient temperature byadding 18.4 grams per liter of iron as ferric sulfate. The pH of theresulting slurry, which was 9.2, was adjusted to 3.5 by the addition of129.7 cc of concentrated hydrochloric acid (specific density 1.18). Theresulting slurry was agitated in cold for 60 minutes. The slurry wasfiltered with suction and the solids washed with water. The washedsolids were removed and dried at 105C. to give a loss on drying of 44.5percent. The combined filtrate and wash analyzed 2.53 grams per litertungsten.

The dried solids, which contained 92.3 percent of the tungsten initiallypresent in the aqueous solution, were found to analyze 51.62 percenttungsten and 12.77 percent iron. The dried solids were reduced atelevated temperature to produce a metallic additive suitable for use insteel-making. The loss in weight on reduction was 34.7 percent. Theresulting metallic additive analyzed:

Tungsten 79.06 percent lron 20.19 percent Phosphorus less than 0.02percent Sulphur 0.1 percent Oxygen 0.30 percent Arsenic less than 6.5ppm The following mass ratios are preferred:

Refractory Fe/Ref. NhJRef. C/Ref. Metal Metal Metal Metal Vanadium0.l:l.0 to 1.0:l.0 to 0.65:) to

0.25:) 104:1.0 0.l:l.0 Tungsten 0.1:].0 tn 0.0S:l.0 In 0.l: l.0

o.s=|.o 0.21m

Molybdenum 0.l:l.0 In 0.l:l.0 to

tion containing a refractory metal in the highest state of oxidation,dispersing finely divided carbon in said solution in an amountsufficient to provide a carbon to refractory metal mass ratio in therange of about 0.6:].0 to 0.8:l.0, adding to said solution a ferric saltof a strong mineral acid in an amount sufficient to provide an iron torefractory metal mass ratio in the range of about 0.1:].0 to 1.0:].0,precipitating an ironrefractory metal-containing complex at a pH in therange of 2.5 to 4.0, in the presence of ammonium ion in an amount toprovide an ammonium to refractory metal mass ratio in the range of0.05:1.0 to 1.6:1.0, and recovering a precipitated refractory metalcomplex intimately admixed with carbon from the aqueous solution.

2. The method in accordance with claim 1 in which said refractory metalis vanadium, molybdenum, or tungsten.

3. The method in accordance with claim 1 in which said refractory metalis vanadium.

4. The method in accordance with claim 3 in which said ammonium isprovided by the addition of an ammonium salt of common anion with saidferric salt.

The method in accordance with claim 4 in which said iron to vanadiummass ratio is in the range of about the precipitation is carried out ata pH within the range o f 3.0 to 3.5. q

9. The method in accordance with claim 8 in which said ammonium anion isthe chloride ion. 7

10. The method in accordance withclaim 2 in which said aqueous solution,after recovery of said complex, is further treated by the addition of aferric salt in an amount sufficient to provide an iron to refractorymetal mass ratio in the range of about 0.5:1.0 to 3.0:].0, and includingthe steps of precipitating a secondary ironrefractory metal complex andrecovering said secondary complex from said aqueous solution.

11. The method in accordance with claim 10 including the steps ofdissolving said secondary complex in an aqueous solution of strongmineral acid, and recycling said dissolved complex to the initialprecipitation step.

12. The method in accordance with claim 11 in which said strong mineralacid is of'common anion with said ferric salt.

13. The method in accordance with claim 12 in which said aqueoussolution of strong mineral acid is a solution containing said refractorymetal in its highest state of oxidation.

14. The method in accordance with claim 1 in which said refractory'metalis molybdenum.

15. The method in accordance with claim 14 in which said ironto'molybdenum mass ratio is in the range of about'0.l:l.0 to 0.6:1.0.'

16. The method in accordance with claim 15 in which said ammonium tomolybdenum mass ratio is in the range of about 0.1:l.0 to 0.2:].0.

17. The method in accordance with claim 16 in which the precipitationiscarried out at a pH within the range of 3.0 to 3.5.

18. The method in accordance with claim 1 in which said refractory.metal is tungsten.

19. The method in accordance with claim 18 in range of about 0.05:1.0 to0.21.0. which said iron to tungsten mass ratio is in the range of 21.The method in accordance with claim 20 in about 0.1:].0 to 0.3:1.0.which the precipitation is carried out at a pH within the 20. The methodin accordance with claim 18 in range of 3.0 to 3.5. which said ammoniumto tungsten mass ratio is in the Po-wso UNITED STATES PATENT, OFFICECERTIFICATE OF CORRECTION Patent No. 3 .75s..65 Deted: September 11,1973 Inventor(s) Milos VOjkOViC V l v I It is certified thaterrorappeairsin the above-identified patent and that said Letters Patentare hereby Corrected as shown below:

Column 1, line 28, the word "liquid'f should be -liquor--. Column 2,1ine23, '"roti os" shouldjbe --ra. cio s -'-t- Column 3, line 16, "THe"should be written --The Column 5, in the table at line 45, finthe thirdcolumn, "Nh /Ref." should read -'--NH /Ref. "In the second line underthis reference "104:1.0" should be -1.4,:1.0--. In

the last column, under C/Ref. the third line- "0.8:l.0" should bedeleted. V h V Signed and sealed this 9th day of April 19714..

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Y t l l C. MARSHALL :DANN Attesting OfficerCommissioner ofPatents

2. The method in accordance with claim 1 in which said refractory metalis vanadium, molybdenum, or tungsten.
 3. The method in accordance withclaim 1 in which said refractory metal is vanadium.
 4. The method inaccordance with claim 3 in which said ammonium is provided by theaddition of an ammonium salt of common anion with said ferric salt. 5.The method in accordance with claim 4 in which said iron to vanadiummass ratio is in the range of about 0.10:1.0 to 0.25: 1.0.
 6. The methodin accordance with claim 5 in which said ammonium to vanadium mass ratiois in the range of about 1.0:1.0 to 1.4: 1.0.
 7. The method inaccordance with claim 6 in which said carbon to vanadium mass ratio isin the range of about 0.65:1.0 to 0.8:1.0.
 8. The method in accordancewith claim 7 in which the precipitation is carried out at a pH withinthe range of 3.0 to 3.5.
 9. The method in accordance with claim 8 inwhich said ammonium anion is the chloride ion.
 10. The method inaccordance with claim 2 in which said aqueous solution, after recoveryof said complex, is further treated by the addition of a ferric salt inan amount sufficient to provide an iron to refractory metal mass ratioin the range of about 0.5: 1.0 to 3.0:1.0, and including the steps ofprecipitating a secondary iron-refractory metal complex and recoveringsaid secondary complex from said aqueous solution.
 11. The method inaccordance with claim 10 including the steps of dissolving saidsecondary complex in an aqueous solution of strong mineral acid, andrecycling said dissolved complex to the initial precipitation step. 12.The method in accordance with claim 11 in which said strong mineral acidis of common anion with said ferric salt.
 13. The method in accordancewith claim 12 in which said aqueous solution of strong mineral acid is asolution containing said refractory metal in its highest state ofoxidation.
 14. The method in accordance with claim 1 in which saidrefractory metal is molybdenum.
 15. The method in accordance with claim14 in which said iron to molybdenum mass ratio is in the range of about0.1:1.0 to 0.6: 1.0.
 16. The method in accordance with claim 15 in whichsaid ammonium to molybdenum mass ratio is in the range of about 0.1: 1.0to 0.2:1.0.
 17. The method in accordance with claim 16 in which theprecipitation is carried out at a pH within the range of 3.0 to 3.5. 18.The method in accordance with claim 1 in which said refractory metal istungsten.
 19. The method in accordance with claim 18 in which said ironto tungsten mass ratio is in the range of about 0.1:1.0 to 0.3:1.0. 20.The method in accordance with claim 18 in which said ammonium totungsten mass ratio is in the range of about 0.05:1.0 to 0.2:1.0. 21.The method in accordance with claim 20 in which the precipitation iscarried out at a pH within the range of 3.0 to 3.5.